/* vsprintf example */
#include <stdio.h>
#include <stdarg.h>

void PrintFError(char *format, ...)
{
  char buffer[256];
  va_list args;
  va_start(args, format);
  vsprintf(buffer, format, args);
  perror(buffer);
  va_end(args);
}

int main()
{
   FILE *pFile;
   char szFileName[] = "myfile.txt";
   int firstchar = (int)'#';

   pFile = fopen(szFileName, "r");
   if (pFile == NULL)
     PrintFError("Error opening '%s'", szFileName);
   else {
     // file successfully open
     fclose(pFile);
   }
   return 0;
}